Underreamer



Nov, 21, 1939. G. M. BOULTER 2,180,452

UNDERREAMER Filed Oct. 1, 1937 I I S INVENTOR. GEoRaE M Bo UL TER.

A TTORNEY.

Patented Nov. 21, 1939 UNITED STATES UNDERREAMER George M. Boult er, Bakersfield. Calife Application October 1,

1 Claim.

This invention relates to oil well drilling tools and more particularly to an underreamer or Wall scraper for scraping and enlarging the bore of the well.

The general object of the invention is to provide an improved underreamer which is simple in construction, inexpensive and efficient in operation.

A more particular object is to provide an underreamer which will provide forcirculation of fluid below its cutters.

A further object is to provide an underreamer in which the cutting blades are prevented from opening the wrong way and mutilating the wall casing.

A further object is to provide an underreamer with improved means for positively expanding its blades into cutting position.

Other objects and advantages will appear hereinafter.

The invention is illustrated in the annexed drawing which forms a part of this specification and in which:

Fig. l is a longitudinal vertical section of my invention showing the scraper blades contracted to inoperative position.

Fig. 2 is a view like Fig. l, but taken at right angles thereto.

Fig. 3 is a fragmentary longitudinal section of the lower portion of my invention showing the scraper blades expanded into scraping position.

Fig. 4 is a cross section of my invention taken on line 4- of Fig. 1.

Fig. 5 is a cross section taken on line 5-5 of Fig. 1.

Fig. 6 is a cross section taken on line 6-6 of Fig. 1. r

Fig. '7 is an end view of the piston shank.

Referring more particularly .to the drawing in which corresponding parts are designated by the same reference characters in all the figures. l designates a body formed with a plunger bore 2 extending through. the upper end thereof, a scraper blade slot 3 extending diametrically through said body below the lower end of said bore, and a pair of pivot bores 4 extending from opposite sides of the body I to the slot 3. The

lower end of the body l is formed with a bit 5 while the upper end of the body is formed with a threaded box 6 to receive a pin on the lower end of a tool string for securing said body on said end of said tool string.

In the bore 2 is mounted a slidable plunger 1 formed at its lower end with a depending shank 8 which extends downwardly through the lower 1937, Serial N 'o. 166.818

end of the plunger bore 2 into the upper portion of the scraper blade slot 3. The shank 8 is formed at its lower end with a pair of forked prongs 9 which are ofiset laterally from each other, the inner faces l0 thereof coinciding along. 5 the axis of said shank and the axis of the plunger l. Rabbets H are formed in opposite edges of the shank 8 into which extend the inner ends of a pair of pins l2 which are screw seated in a body l'as at E3, said pins preventing rotation of the 10 plunger 1 and its shank 8. A bore l4 extends longitudinally through the plunger 1 and its shank 8 for the circulation of water therethrough, The piston 1 is formed with an upstanding stud I5 and a lower external flange I6 15 for mounting a packing seal IT comprising a leather cup 18, a follower IQ for said cup, and a leather cup 213 resting upon said follower. The upper end of the plunger stud I5 is threaded at 2| and a sleeve nut 22 is threaded internally at 20 its lower end at 23 for engaging said stud thread, so that the lower end of said nut may be screwed down against the leather cup 20 for tightening up and holding the packing seal I! in position on the plunger 1. 25

In the slot 3 are pivotally mounted a pair of scraper blades 24 by means of a pair of pivotstuds 25, which are tightly fitted in the pivot bores 4 and extend into bearing openings 26 in the scraper blades 25. Said pivot studs are secured in said pivot bores by set' screws 21 seated in the body I. Each scraper blade 24 is formed with a recess 28 in its inner side to receive a prong 9 of the plunger shank 8, which recess is bounded by a straight wall 29 and an inclined wall 30. Each scraper blade is also formed with a channel 3| leading from the recess 28 in the blade through one edge of the blade. Each blade 24 is formed with scraping edges 32 and 33.

The operation of my invention is as follows:

When there is no fluid under pressure in the plunger bore 2 the scraper blades 24 are swung down of their own weight, on their pivots 25 within the slot 3 in the body I, into their contracted position, as shown in Figs. 1 and 2 of 45 the drawing, and the plunger 1 is moved up to its uppermost position by the engagement of the corners 34, between the recess walls 29 and 30 of the scraper blades 24, with the lower ends of the shank prongs 9.

Upon the introduction of fluid under pressure through the tool string into the upper end of the plunger bore 2, the plunger 1 is forced downwardly in the plunger bore 2 which causes the lower ends of prongs 9 to engage the corners 34 55 of the blade recesses 28 and swing the scraper blades 24 on their pivots 25 outwardly through the slot 3 beyond the sides of the body I into the position shown in Fig. 3, in which position the scraping edge 32 of the blades 24 are in position to scrape the sides of the well hole while the lower cutting edges 33 are in position to the wall of the well hole below the blades. Some of the v fluid introduced into the body bore 2 is circulated through the plunger bore M, the registering channels 3| in the blades 24, and the slot 3, into the well hole over the blades and up around the body I and the tool string and out of the well.

I claim:

An underreamer comprising a body, a plunger formed with a depending shank and a pair of prongs on the lower end of said shank, said plunger and shank being provided with a bore extending therethrough, a pair of scraper blades pivotally mounted in said body, said blades being formed with recesses, to receive said prongs, and with circulating channels, and means whereby fluid under pressure is introduced into said body to force said plunger, shank and prongs downwardly in said body, whereby the ends of said prongs are caused to engage the walls of said blade recesses and swing said blades outwardly from said body, and to bring said circulating channels of said blades into register, so that part of the fluid introduced into said body will circulate through said bore in said plunger and shank, and through said registering blade channels, outwardly from said body over said blades.

GEORGE M. BOULTER. 

